Ionic-Potential-Guided Fluoride Engineering of Reversible Mn-Based Cathodes for Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Manganese-based layered oxides are promising for sodium-ion batteries (SIBs) due to high capacity and low cost.
• Structural instability and Jahn-Teller distortion in Mn3+ hinder their practical application.

Purpose of the Study:

• To develop a strategy for enhancing the structural stability and electrochemical performance of P2-type Mn-based layered oxides for SIBs.
• To address challenges of structural instability and Jahn-Teller distortion in Mn-based cathodes.

Main Methods:

• Ionic-potential-guided metal-fluoride engineering by incorporating AlF3 and transition-metal vacancies into a P2-type layered oxide.
• Multiscale characterization and density functional theory (DFT) calculations.
• Electrochemical performance testing (voltage, capacity, cycling stability).

Main Results:

• The dual-site tuning strategy elevated the total ionic potential, enhancing interlayer stability and suppressing Jahn-Teller effects.
• A reversible, solid-solution Na+ (de)intercalation mechanism was observed with negligible lattice strain and suppressed Mn3+ formation.
• The optimized cathode achieved a higher average voltage (≈3.60 V), reversible capacity (134 mA h g-1), and improved cycling stability (83% retention after 100 cycles) compared to the pristine material.

Conclusions:

• Ionic-potential-guided AlF3 incorporation is a robust and scalable strategy for designing high-performance cathodes for next-generation SIBs.
• This approach successfully enhances structural integrity and electrochemical properties, overcoming limitations of traditional Mn-based materials.